DOE OSTI2020
Tb2Ni12P7 crystallizes in the hexagonal P-6 space group. The structure is three-dimensional. there are two inequivalent Tb3+ sites. In the first Tb3+ site, Tb3+ is bonded to six equivalent P3- atoms to form distorted TbP6 pentagonal pyramids that share corners with six equivalent NiP5 square pyramids, corners with twelve NiP4 tetrahedra, edges with twelve NiP4 tetrahedra, and faces with two equivalent TbP6 pentagonal pyramids. All Tb–P bond lengths are 2.89 Å. In the second Tb3+ site, Tb3+ is bonded to six equivalent P3- atoms to form distorted TbP6 pentagonal pyramids that share corners with six equivalent NiP5 square pyramids, corners with twelve NiP4 tetrahedra, edges with three equivalent NiP5 square pyramids, edges with nine NiP4 tetrahedra, and faces with two equivalent TbP6 pentagonal pyramids. All Tb–P bond lengths are 2.87 Å. There are four inequivalent Ni+1.25+ sites. In the first Ni+1.25+ site, Ni+1.25+ is bonded to four P3- atoms to form NiP4 tetrahedra that share corners with two equivalent TbP6 pentagonal pyramids, corners with two equivalent NiP5 square pyramids, corners with twelve NiP4 tetrahedra, edges with three TbP6 pentagonal pyramids, edges with two equivalent NiP5 square pyramids, and edges with three NiP4 tetrahedra. There are a spread of Ni–P bond distances ranging from 2.25–2.33 Å. In the second Ni+1.25+ site, Ni+1.25+ is bonded to four P3- atoms to form NiP4 tetrahedra that share corners with four TbP6 pentagonal pyramids, corners with two equivalent NiP5 square pyramids, corners with ten NiP4 tetrahedra, an edgeedge with one TbP6 pentagonal pyramid, edges with four equivalent NiP5 square pyramids, and edges with three NiP4 tetrahedra. There are a spread of Ni–P bond distances ranging from 2.15–2.32 Å. In the third Ni+1.25+ site, Ni+1.25+ is bonded to four P3- atoms to form NiP4 tetrahedra that share corners with two equivalent TbP6 pentagonal pyramids, corners with four equivalent NiP5 square pyramids, corners with ten NiP4 tetrahedra, edges with three TbP6 pentagonal pyramids, an edgeedge with one NiP5 square pyramid, and edges with four NiP4 tetrahedra. There are a spread of Ni–P bond distances ranging from 2.27–2.35 Å. In the fourth Ni+1.25+ site, Ni+1.25+ is bonded to five P3- atoms to form distorted NiP5 square pyramids that share corners with four TbP6 pentagonal pyramids, corners with four equivalent NiP5 square pyramids, corners with eight NiP4 tetrahedra, an edgeedge with one TbP6 pentagonal pyramid, edges with four equivalent NiP5 square pyramids, and edges with seven NiP4 tetrahedra. There are a spread of Ni–P bond distances ranging from 2.27–2.55 Å. There are three inequivalent P3- sites. In the first P3- site, P3- is bonded in a 9-coordinate geometry to two equivalent Tb3+ and seven Ni+1.25+ atoms. In the second P3- site, P3- is bonded in a 9-coordinate geometry to two equivalent Tb3+ and seven Ni+1.25+ atoms. In the third P3- site, P3- is bonded in a 3-coordinate geometry to nine Ni+1.25+ atoms.